+

The Nervous System

Chapter 29.1 and 29.2

+Learning Objectives:

To be able to: Explain the composition of the nervous system and

how organ systems communicate To identify the main features of a neuron

Stimulus, Central nervous system, Peripheral nervous system, Neuron, Dendrite, Axon

Keywords:

+The nervous system is a physically connected network of cells, tissues and organs that controls thoughts, movements and simpler life processes such as swallowing. For example, when you walk outside on a sunny day without sunglasses, your nervous system senses the bright light and sends messages that tell your pupils to shrink.  The endocrine system is a collection physically disconnected organs that helps to control growth, development and responses to your environment. - Can you give me an example?

+What is the nervous system?

+What is the nervous system?The Nervous System is split into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

The CNS is the brain and spinal cord.

The PNS transmits electrical impulses to and from the CNS.

+In your books…

Use page 820 to answer the following questions: What is a neuron? What is the FUNCTION of a neuron? How many types of neurons are there and what are

their functions?

+Check your answers! What is a neuron?

A neuron is a highly specialized cell

What is the FUNCTION of a neuron?

A neuron receives and transmits signals. It stores information and carries messages within the nervous system and between other body systems

How many types of neurons are there and what are their functions?

- Sensory: detect stimuli & transmit signals to CNS

- interneuron (relay): receive signals from sensory neurons & relay them within CNS

- motor: pass messages from nervous system to other tissues in body

What are the functions of: The cell body? Dendrites? Axons?

Use page 820 to help you

The Stimulus-Response ModelThe basic pathway for a nerve impulse is described by the stimulus-response model

A receptor converts a stimulus into a nerve impulse, which is transmitted by a sensory neuron to the CNS (spinal cord)Relay neurons within the CNS will transmit this signal to a control centre (usually the brain), where the information is processedMotor neurons will transmit a resultant nerve impulse from the CNS to an effector organ (a muscle or gland), eliciting an appropriate response

+Voluntary and Involuntary Responses

Voluntary responses are things that you can control, for example picking up a pen, kicking a ball.

Your brain sends an impulse down the spinal cord which then passes an impulse to your motor neurones to complete the action.

+Voluntary and Involuntary Responses

Involuntary responses are things you can’t control.

These are how you react to pain, your eyes dilating and contracting, your heart beating etc.

+ReflexA reflex is a rapid and involuntary response to a stimulus and results from an even simpler pathway called a 'reflex arc'

Reflex actions do not involve the brain in the decision making process - instead sensory information is relayed directly to motor pathways within the spineThis results in a reaction without conscious thought, which may be important in survival situations when quick reactions are necessary to avoid permanent damage or pain

+ The Reflex Arc

PNS CNS

+The Reflex ArcCopy and complete:

When you stand on a pin, the pain sensor sends an electrical impulse along the sensory neuron. This is passed across a synapse as a chemical and processed in the CNS in a relay neuron. It is passed across another synapse and through the motor neuron as an electrical impulse. This causes the muscle to move. It is an involuntary response.

CNS motor synapse electrical involuntary

sensor

+The Reflex ArcCopy and complete:

When you stand on a pin, the pain sensor sends and electrical impulse along the sensory neuron. This is passed across a synapse as a chemical and processed in the CNS in a relay neuron. It is passed across another synapse and through the motor neuron as an electrical impulse. This causes the muscle to move. It is an involuntary response.

CNS motor synapse electrical involuntary

sensor